1. Field of the Invention
The present invention relates to a process of producing an antimony-containing oxide catalyst. More specifically, the present invention relates to a process of producing an antimony-containing oxide catalyst having excellent activity which is useful for oxidation, oxidative dehydrogenation or ammoxidation of olefins.
2. Description of the Prior Art
It is well known that antimony-containing oxide catalysts, more specifically, catalysts comprising oxides of antimony and at least one metal selected from the group consisting of iron, cobalt, nickel, manganese, uranium, tin and copper are useful in the production of unsaturated aldehydes by oxidation of olefins, the production of diolefins by an oxidative dehydrogenation of olefins and the production of .alpha.-unsaturated nitriles by ammoxidation of olefins. Referring to the production of acrylonitrile by ammoxidation of propylene, for example, a catalyst comprising oxides of antimony and iron, cobalt or nickel is described in Japanese Patent Publication No. 19111/63; a catalyst comprising oxides of antimony and tin is described in U.S. Pat. No. 3,152,170; a catalyst comprising oxides of antimony and uranium is described in U.S. Pat. No. 3,198,750; and a catalyst comprising oxides of antimony and manganese or copper is described in British Pat. No. 987,960.
However, these catalysts are not satisfactory from the standpoint of the yield of the desired products obtained. Improvements have thus been made by adding certain other elemental components to these catalysts. Further, a multi-component catalyst comprising oxides of antimony and other metals which is obtained by adding an oxide of at least one metal selected from the group consisting of molybdenum, vanadium and tungsten, and tellurium to any of an oxide of antimony and iron, an oxide of antimont and tin, and an oxide of antimony and uranium, respectively, is described in U.S. Pat. No. 3,668,147 and Japanese Patent Publication Nos. 40958/72 and 19764/72. However, the greatest care must be taken in the production of a multi-component catalyst comprising antimony-other metal oxides. In order for the composition of an antimony and another metal oxide as a basic catalyst to act effectively as a catalyst in respective reactions of the oxidation of, the oxidative dehydrogenation of and the ammoxidation of olefins, first of all, it is required for each component to be bound in the form of either a solid solution or a specific oxide compound. Phrased differently, the efficiency of the catalyst is not simply determined only by the composition of active components in the catalyst but a method suitable for the production of the catalyst having the bonding as described above must be employed.
In the production of a catalyst comprising oxides, various compounds can be used as raw materials for antimony. From an industrial standpoint, however, antimony oxides (i.e., antimony trioxide, antimony tetroxide and antimony pentoxide) or metallic antimony powder are preferably used. In using these oxides as raw materials for antimony, in order to react the antimony compounds with the polyvalent metal compounds described above the temperature employed depends on the methods for the production of the catalysts utilized. However, in general, high temperatures, e.g., 500.degree. C. to 1100.degree. C., are required. That is, unless antimony-other metal oxide catalysts are calcined at high temperatures, the desired activity of the catalysts is not obtained.
Further, it has now been found that unless all of the additive components described above form a solid solution with the antimony-other metal oxides which are bound in a specific way as described above, the desired activity of the catalyst is not obtained in a multi-component catalyst comprising antimony-other metal oxides which is obtained by adding at least one compound of a metal selected from the group consisting of molybdenum, vanadium and tungsten and also a tellurium compound to an oxide of antimony and the polyvalent metal described hereinbefore (hereafter merely referred to as "antimony-polyvalent metal oxide").
However, some of the additive compounds in the antimony-polyvalent metal oxide catalyst give rise to differences from the antimony-polyvalent metal oxides as a basic catalyst, in the mutual reactivity thereof at high temperatures. For example, antimony-polyvalent metal oxides as a basic catalyst are difficult to sinter and require calcination at high temperatures as mentioned above. On the other hand, some of the additives described above are easily sintered and even readily vaporize. If attempts are made to form a solid solution of the additive compounds in the antimony-polyvalent metal oxides by the reaction of the antimony-polyvalent metal oxides and the additive compounds, which have these differences in properties as described above, various serious problems occur so that very severe conditions for the production of the catalysts are required. For instance, it has been found that in the case of mixing the additive compounds with the basic catalyst components in the preparation of catalysts in accordance with conventional methods, especially where a large amount of the additive compounds are added, the efficiency and physical properties of the catalysts obtained vary greatly even with slight changes in calcination temperatures and therefore, it is extremely difficult to consistently produce catalysts having the desired activity and physical properties.